1. Field of the Invention
The present invention relates to an improved method of and an improved apparatus for manufacturing a metallic fiber, which is used advantageously as a filter, an electromagnetic shielding member, an antistatic member or the like, and to a method of and an apparatus for manufacturing the twine of metallic fibers, which is used in a product such as a belt, catalyst carrier or the like. Further, the present invention relates to a metallic fiber, in particular, a steel fiber, and the twine of metallic fibers manufactured in accordance with the above-described method. Also, the present invention relates to a method of manufacturing a color stainless steel fiber in which the color of textile can be freely selected, i.e., a color stainless steel fiber in which the mix spinning with an organic fiber or an inorganic fiber is allowed and which is useful in the fields of decoration and craft.
In general, as a technology of manufacturing inexpensively a metallic fiber whose diameter is 50 .mu.m or less, it has been widely used that a plurality of metal wires is coated by a metallic tube member or a metallic plate member, and is extended by drawing in which the metal wires are penetrated through a die and the diameters thereof decrease. Further, the plurality of extended wires is bound and coated again by the metallic tube member or the metallic plate member and extended. The diameter of metal wire is sufficiently decreased so as to form a metallic fiber. Next, a metallic coating member, i.e., a matrix member, formed by the tube member or the plate member is dissolved by acid and removed from the extended wire, i.e., convergent extended wire, which encloses the metallic fiber. The metallic fiber is thereby obtained.
In addition, in order to form a twine from the obtained metallic fiber, the metallic fibers are bound, and the plurality of bound fibers subjected to a primary twist is at first subjected to a secondary twist.
Moreover, conventionally, a stainless steel fiber which may be extra fine is mainly kneaded with a conductive cloth, a refractory cloth, a plastic or the like and is used for interior materials or industrial applications such as a filler, a filter of filtration device, or the like which improve conductivity or thermal conductivity of the cloth. Consequently, the appearance of the stainless steel fiber was not greatly demanded. The stainless steel fiber which is used for these conventional applications is manufactured by convergent extension or excision, such that the color thereof is simply silver of the stainless steel. Accordingly, the expansion of application in which the good appearance of the stainless steel is demanded is actually impeded.
2. Description of the Related Art
So far, in a case in which the matrix member of a convergent fiber material is dissolved so as to obtain a metallic fiber, a method of submerging the matrix member in a solution such as a nitric acid is known as the method of dissolving a matrix member. For example, Japanese Patent Application Laid-Open (JP-A) No. 61-137623 (a method of manufacturing a stainless fiber) discloses a method of submerging a matrix member in a thermal nitric acid solution, and then dissolving and removing the matrix member from the convergent fiber material. Also, Japanese Patent Publication (JP-B) No. 53-34589 (a method of manufacturing a stainless metallic fiber) discloses a method of submerging a convergent extended wire in a nitric acid solution so as to dissolve and remove a matrix member (an armoring material) from the convergent extended wire, and thereafter, submerging instantaneously the convergent extended wire in a mixed solution of hydrofluoric acid and nitride acid.
Because highly reactive chemicals are used, these chemically dissolving methods required dangerous operations. At the same time, there were a drawback of environmental pollution due to the generation of NO.sub.x gas and a drawback of processing waste acid. Further, it was difficult to maintain the conditions of dissolution within a predetermined range.
On the other hand, a method of dissolving a matrix member electrochemically is known.
For example, there is a method of dissolving a matrix member electrically by direct feeding. In this case, feeding to a convergent extended wire is effected by contacting a feed roll or the like.
One of the conventional examples of direct feeding method uses conventional presser rolls, and the explanatory view of the feeding method is shown in FIG. 1. As shown in FIG. 1, as a convergent extended wire 2 is bent and nipped by a feed roll 3 and presser rolls 4, which are positioned in front of and in rear of the feed roll 3, desirable contact between the convergent extended wire 2 and the feed roll 3 is achieved. FIG. 1 shows an electrolytic tank 1.
In this feeding method, when the convergent extended wire 2 passes between the presser rolls 4 and the feed roll 3, the convergent extended wire 2 is subjected to bending. Accordingly, tension generates in the convergent extended wire 2.
Tension, which is generated due to the bending by the feeding portion and which gradually increases in the traveling direction of the convergent extended wire, becomes greater than the tensile strength at break of the convergent extended wire, which gradually decreases in a stage in which the matrix member of the convergent extended wire is being electrically dissolved. As a result, there was a drawback in that the wire is broken during the electrolytic processing.
In a stage in which the matrix member of convergent extended wire is electrically dissolved, when the metallic fibers start to expose, the tensile strength at break of each of the metallic fibers becomes extremely small. Thus, reduction in the tension generated at the convergent extended wire during the traveling thereof becomes particularly important.
As means of reducing the tension generated at the convergent extended wire during the traveling thereof, FIG. 2 shows the explanatory view of a pendulum-type feeding method. As shown in FIG. 2, a structure is formed by a supporting member 5, a pendulum-type feed roll 6 which is rotatably supported by the supporting member 5, and receiving rolls 7. The feeding to a convergent extended wire 2 is effected by contacting the pendulum-type feed roll 6 with the upper portion of the convergent extended wire 2 by the weight of the feed roll 6. In this method, excessive contact pressure is not imparted at the convergent extended wire 2 and the tension generated thereat is not great. However, it is difficult to avoid the vibrations of convergent extended wire 2 at the time of passing between the feed roll 6 and the receiving rolls 7, and due to the vibrations, the pendulum-type feed roll 6 also vibrates in the vertical direction. Consequently, there was a drawback in that the contact pressure between the convergent extended wire 2 and the pendulum-type feed roll 6 varies and that stable feeding cannot be performed.
Further, FIG. 3 shows the explanatory view of a case in which a plurality of convergent extended wires are fed by one pendulum-type feed roll. In a case in which a plurality of convergent extended wires are fed by one pendulum-type feed roll 6, the tension of each of the convergent extended wires 2 is different. Accordingly, there was a drawback in that slack occurs at the convergent extended wire 2' whose tension is small such that the convergent extended wire 2' does not contact correctly the pendulum-type feed roll 6.
In this way, since there are various drawbacks in the method of electrical dissolution by direct feeding, an indirect feeding method has been considered as well.
For example, EP 0337517B1 discloses a method in which a plurality of electrolytic tanks are provided, a plurality of electrodes are disposed at the lower portion of the tanks so that a convergent extended wire pass through the electrodes, positive and negative potentials are alternately applied to the plurality of electrodes arranged in the passing direction of the convergent extended wire, so that the matrix member of the convergent extended wires is electrolytically removed by indirect feeding.
In this indirect feeding method, there was no drawback caused by the feeding portion as in the aforementioned direct feeding methods. However, the convergent extended wire alternately becomes a cathode and an anode repeatedly during the electrolytic processing, and the matrix member is not dissolved in the cathode processing. Thus, the method was inefficient, and there was a drawback in that it is difficult to control the anode electrolytic conditions under the power supply voltage.
The first aspect of the present invention solved advantageously the above drawbacks, and the object thereof is to provide a method of and an apparatus for manufacturing a metallic fiber which dissolves and removes desirably the matrix member of a convergent extended wire by an electrolytic processing which is based on a direct feeding method and which does not generate harmful gas.
Further, with regard to manufacturing of the twine of metallic fibers, in the conventional methods, the elongation of metallic fibers is small as compared to that of organic fibers. As a result, when the fibers are twined, the fibers are broken due to the friction with a guide, and the fluffiness of twine is generated. Accordingly, the appearance of twine is deteriorated, the diameter thereof is increased, and therefore, these become drawbacks when the twine is woven into a cloth. When the twine is slack, a kink occurs due to the unwinding of twine and becomes an obstacle in subsequent manufacturing. The problem of generation of kinks due to the unwinding is especially noticeable when the thread is twined singly and not twined primarily for preventing fluffiness. In this case, subsequent manufacturing may not be carried out.
The second aspect of the present invention was developed in light of the above-described conventional art, and the object thereof is to provide the twine of metallic fibers which does not have fluffiness, which is strong, and which is not unwound. Further, the object thereof is to provide means of manufacturing the twine having such characteristics by a relatively simple method.
Conventionally, except for the case in which a silver metallic luster is used, it was inappropriate that the twine is mixedly spun or mixedly woven with dyed organic fibers. Additionally, in a case in which the twine is used as a thread for winding around a fly for fishing and adjusting buoyancy, the color of silver was not proper. Moreover, a plastic may be used as a cabinet for electronic components. At this time, from the point of view of preventing the drawbacks of electromagnetic wave, metallic fibers are mixed with the plastic. However, due to the difference in colors of the two, the appearance of cabinet was poor.
On the other hand, the method of coloring the stainless steel has been proposed. For example, Japanese Patent Application Laid-Open (JP-A) No. 2-107798 discloses a method of coloring the stainless steel electrochemically by applying a pulse potential thereto.
However, in the above-disclosed coloring method, the stainless steel to be colored is a billet. When the above-described coloring method is applied to the bundle of plurality of stainless steel fibers having the diameters of 4 to 50 .mu.m, the fibers are broken due to the friction with a guide roll or a submerge roll, and the bundle of fibers becomes fluffy. There were drawbacks of reduction in the strength of fibers, deterioration of the appearance thereof, or the like. Moreover, in a case in which it is difficult for the electrolyte to penetrate through the interior of the bundle of fibers, there was a drawback in that the irregularities in color occurs.
Accordingly, the object of the third aspect of the present invention is to provide a color stainless steel fiber whose surface is satisfactorily colored and which does not have the above-described drawbacks, and to the method of manufacturing such color stainless steel fiber.